Variable displacement rotary pump



Dec. 6, 1949 D. c. CLARKE 2,490,115

vmuaw nrsrmciaunuw ROTARY rumr Filed Oct. 28, 1942 3 Sheets-Sheet l 75 75 as Y 1 GUT INVENTOR. Wi s [f flarffe Dec. 6, 1949 I c, CLARKE 2,490,115

VARIABLE DISPLACEMENT ROTARY PUMP Filed Oct. 28, 1942 s Sheets-Sheet z INVENTOR. Jag/gs 6 (Jar/Q HTTOR/VE)" Dec. 6, 1949 D. c. CLARKE 2,490,115

VARIABLE msrucnuau'r BOZ ARY PM? 4 Filed on. 28, 1942 s Sheets-Sheet s wf $3M;

' mmvmx. Wins (3 Clarke niromvsy Patented Dec. 1949 Douglas C. Clarke, Mountain Lakes, N. J assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation oi Delaware Application October 28, 1942, Serial No. 463,693

1 Claim.

This invention relates to pumps and particularly to a rotary pump of the variable displacement type.

.It is known in the art that a pump of the spur gear type may be operated as a variable displacement pump by providing means for shifting one of the working gears along its axis of rotation to vary that portion of the width of the gear face having actual contact with the companion gear. In actual practice, however, it is extremely difiicult to secure variable displacement in this fashion because of the fact that inter-engaged rotating spur gears olfer great resistance to axial dis placement of either of such gears. The present invention is characterized by the employment of a difierent method for securing variation in the amount of fluid displaced by a pump of the gear type; the different method herein disclosed involving use of eccentrically inter-engaging gears. together with means for varying the eccentric relationship of one of said gears with respect to another.

An object of the invention therefore is to provide, in a pump of the eccentrically meshing gear type, novel means for varying the pump displacement.

Another object is to provide, in a pump of the character indicated, novel pressure responsive means for varying the pump displacement.

Another object is to provide a novel compound pump in which each component pump is constituted by a set of eccentrically inter-engaging gear elements.

These and other objects of the invention will become apparent from inspection of the following specification when read with reference to the accompanying drawings wherein is illustrated the preferred embodiment of the invention. It is to be expressly understood, however, that the drawings are for the purpose of illustration only, and are not designed as a definition of the limits of the invention, reference being had to the appended claim for this purpose.

In the drawings:

Fig. 1 is a longitudinal sectional view of a pump unit embodying the invention;

Fig. 2 is a longitudinal sectional view at right angles to the view of Fig. 1;

Fig. 3 is a transverse sectional view along line 3--3 of Fig. 1;

Fig. 4 is a transverse sectional view along line 4-4 of Fig. 2;

Fig. 5 is an end view looking from the right of Fig. 1;

Fig. 6 is a view in elevation of a ported plate 2 which is interposed between first and second pumps of the unit;

Figs. 7, 8, 9 and 10 are views of the relationship existing between the inner and outer gear elements of the first component pump of the unit as the center of the controlling eccentric surface is progressively varied;

Figs. 7a, 8a, 9a and 10a are diagrams indicating thedegree of overlapping between the respective suction and pressure cycles of the two components of the pump as the position of the center of the eccentric surface is varied progressively from the x1 position of Fig. '7 to the "034 position of Fig. 10; and

Fig. 11 is a diagrammatic showing of the hy draulic circuit which controls the automatic shifting of the center of the eccentric surface, in accordance with pressure variations.

In the drawings, reference characters is and i6 designate the inner and outer rotors constituting the first component of the pump, and reference characters I! and I8 designate the inner and outer rotors constituting the second compon nt, while reference character it! designates the common actuating shaft for both components of the pump; the rotors l5 and I! as well as the intervening connecting plate 2! and the outer plate 24% being suitably secured to the shaft IQ for rotation as a unit therewith. The shaft i9 is in turn driven by the transmission element 22 which has teeth or splines 23 adapted to be engaged with corresponding teeth or splines of the prime mover (not shown) which is the source of power for rotation of the pump.

As indicated in Figs. 7, 8, 9 and 10 (with particular reference to rotors l5 and [6) each inner rotor has a number of teeth which is one less than that of the outer rotor which it drives and which rotates about an axis eccentric thereto, as in patent to Hill No. 1,682,563; but while the meshing relationship between rotors I! and I8 remains fixed, the meshing relationship between rotors I5 and I6 is adapted to be shifted in accordance with variations in the pressure developed by the pump. As shown, the shifting means includes a shiftable control ring 26 having teeth 21 in engagement with corresponding teeth on a pinion 28 which cooperates with the shifter ring 2t in such manner as to constitute, in efi'ect, a gear type of hydraulic motor adapted to rotate to a limited extent, and in either one direction or the other according to whether pressure fluid is applied thereto by way of the port 3| (see Fig. 11) or the port 32, each of which ports is adapted to receive pressure fluid at alternate times by reason of intermittently established connection with the outlet chamber 36 of the pump, while a parallel connection with the inlet chamber 33 of the pump serves to provide a path of discharge of fluid from the ports. 3| and 32 at alternate times; the action being controlled by a valve 39, 40. Thus the valve 39, 40 governs the degree and direction of rotation of the pinion 26 and hence the direction of shifting of the axis of the rotation of the outer rotor I6 of the pump.

A spring 4|, the pressure of which is adjustable by turning nut 42, bears against valve head 43 secured to valve plunger 39, and thus opposes movement of the said valve plunger to the right (Fig. 1) the movement of the plunger to the left being limited by shoulder 44 of the valve hous- The valve plunger 39 is slidable in the stationary valve sleeve 40, in which sleeve are provided longitudinally extending ports 5| and 52 and transversely extending ports 6|, 1|, I2, 8|, 9|, and 92; the ports 9| and 92 not being visible in Fig. 1, but the relative locations thereof, in relation to the valve heads 46, 41 and 48, being shown schematically in Fig. 11. Also, as shown schematically in Fig. 11, the ports 9| and 92 lead to passages 53 and 54, respectively, which in turn lead to ports 3| and 32, respectively, in the fluid receiving chambers of the displacement controlling pinion motor 28; while the ports 5| and 52 are shown in Fig. 11 as having communication with the pump ports 36 and 38, by way of conduits 33 and 31, respectively.

Lin-operation, when rotors I5 and I6 are in the relationship indicated in Fig. '|-that is, when shifter ring 26 is so disposed, in relation to pinion 29, that the center of the circle of contact with outer rotor I6 is at the point .11 as shown in Fig. I-the application of torque to shaft I9 will produce a pumping action in which the amount of fluid pumped from inlet 38 to outlet 36 will be approximately twice the capacity of either set of rotors (the rotors I5, |6 or the rotors II, I8) acting alone. This is true because there is, in thisFig. '7 relationship, complete coincidence between the contours of inner rotors I5 and IT on the one hand, and outer rotors I6 and I8, on the other; hence the incoming fluid will fill all suction spaces, since the openings 95, 96, 91, and 98 in plate 2| (see Fig. 1) connectthe suction spaces between rotors I1 and I6 with suction spaces between rotors I5 and I6. For the same reason the fluid delivered to outlet 36 on each complete revolution of the pump shaft 19 will be the quantity "squeezed out by rotors I5 and I6 plus the-quantity squeezed out by rotors I1 and I8, or, in other words, double the output of either set working alone.

Now, however, if the shifter ring 26 is rotated from the Fig. 7 position to that of Fig. 8, 9 or 10, there is a reduction in pump output, because there will no longer be complete coincidence of contours as between rotors I5 and I1, or as between rotors l6 and I6; hence a portion of the liquid will by-pass from one set of rotors to the other, rather than being delivered to the outlet chamber 36. In fact, when the position of Fig. is reached there is a complete by-passing of all liquid entering the pump, as the suction phase of one stage coincides fully with the pressure phase of the other (see the diagram Illa) and the result is to reduce the output of the pump to zero.

Of course, as the output falls off, so also may the pressure acting (through port 6|) upon valv'e of the pump rotors.

plunger 39, and the tendency of valve plunger 39 will be to shift back, under the influence of spring 43, until the pressure in conduit 64 is relieved by way of discharge conduit 31 leading back to the suction side 36 of the pump. When this occurs pinion 26 will receive pressure through line 33 and this will rotate pinion 28, hence ring 26, in the opposite direction, thus restoring pump output toward the maximum condition. Thus the pump automatically adjusts itself to the requirements of the fluid consuming device or devices (not shown) associated therewith.

Novel means to hold the rotating parts in sealing relationship to the housing and to each other comprise the following: a series of springs 62 acting axially against plungers 63 slidable in angularly spaced pockets of an annular plate 64 keyed to the shaft I9, and also acting axially against the rear walls of said pockets, wherefore a sealing pressure is exerted in both axial directions-to the left, against bronze thrust washer 66, through the intervening steel plungers 63; and to the right, against the shoulder 68 of the pump housing, through the intervening rotating parts 64, I5, l6, 2|, l1, l8 and 24. Nut I3, threaded to the end of shaft I9, permits adjustment of the degree of tightness, there being shoulders on the shaft I9 to take the thrust as the nut is turned in the tightening direction. As the pump operates and develops fluid pressure, such fluid pressure is effective in the annular area indicated at 88 in Fig. 1 and in this area the fluid acts in both directions to maintain sealing pressure, thus taking over the function which is performed by the springs 62 during the initial stage of operation. The annular space at 61 (Fig. 1) ermits displacement controlling ring 26 to expand axially, when heated, and thus the danger of binding of the parts is avoided without destroying the sealing properties, as the surfaces between parts 64 and I6, also between parts l6 and 2|, remain tightly sealed by the fluid pressure in the areas 88, as above described. Another novel feature assures against binding This novel feature is the machining of the rotors so that the inner rotors I5 and I! are slightly wider (axially) than the outer rotors I6 and I8, respectively. Therefore, in operation, when the inner rotors expand, upon heating, to a greater degree than the outer rotorsas they will, because the inner parts are subject to the greater temperatures-the working clearances for the outer rotors I6 and I8 will increase. Another novel feature is the fact that the members 24, 2| and 64constituting the side walls of the rotors--rotate with the inner rotors. This provides an important advantage (which is equally important for pumps having only one set of rotors) in that rubbing friction is reduced tremendously. The only appreciable rubbing fric-- tion is at the surface 68, in the illustrated embodiment, but here the wear is taken up by the action of fluid pressure in the several areas 88, as above explained.

All these last-described features are applicable to pumps with a single set of rotors, as well as to the double type illustrated herein.

Screws I3 hold the pump body to the mounting plate I4, and pack ngs I6, retained by a split retainer ring 1'], seal the pump at the driving end. Each plunger 63 also has a packing ring, as indicated at I8. As a precaution against excessive oil within the shaft chamber, there is provided an oil return opening I9 (see Fig. 2) leading back to the inlet side 39. Ports 63 and 64 register I having a fluid inlet and a fluid outlet, at first pump mounted within said housing having an inlet and an outlet and a second pump mounted within said housing having an inlet and an outlet and cooperating with said housing inlet and outlet, said first and second pumps each having an inner pumping rotor and an outer pumping rotor meshingwith said inner rotor and driven thereby, a

driving shaft rotatably mounted in said housing,

said driving shaft keyed to the inner pumping rotors of said first and second pumps, an annular ring rotatably mounted in said housing, said annul-ar ring having an inner circular surface eccentric to the axis of rotation of said shaft and said inner rotors, one of said outer rotors bearing upon the inner surface of said housing and having a fixed axis of rotation, and the other of said outer rotors bearing upon the inner circular surface of said annular ring, means for shifting said annular ring in respect to said shaft and inner rotor of said first pump to vary the rela- 6 tionship between the respective axes of rotation of theouter and inner rotors of the first pump so as to vary the relationship between the fluid inlets and outlets of said first and second pumps for regulating the amount of fluid displaced from the fluid inlet to the fluid outlet of said housing.

DOUGLAS C. CLARKE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name a Date 711,662 Herdman Oct. 21, 1902 1,603,395 Mohl Oct. 19, 1926 1,964,330 Pitt June 26, 1934 1,965,388 Ott July 3, 1934 1,970,146 Hill Aug. 14, 1934 2,042,247 Blood May 26, 1936 2,079,375 McCollum May 4, 1937 2,119,902 Blood June 7, 1938 2,166,423 Clark July 18, 1939 2,234,775 Parsons Mar. 11, 1941 FOREIGN PATENTS Number Country Date 238,886 Great Britain Nov. 19, 1926 848,518 France July 24, 1939 

